What anatomical structure does a coin facing you on a lateral film represent?

A coin facing you on a lateral film represents the trachea because it is a cylindrical structure located in the midline of the neck and thoracic cavity. When imaged laterally, an object like a coin could mimic the lateral profile of the trachea, which appears as a well-defined, circular silhouette.

Additionally, the trachea's location and orientation in the thorax make it a prominent target for imaging studies, as it typically appears in a midline position on lateral radiographs. The trachea is also more likely to present as a round shape in this view compared to other structures, such as the esophagus which has a more irregular contour and lies slightly to the left of the midline in most people, or the heart, which is more complex in shape and oriented at a diagonal in the thoracic cavity. The spinal column would not appear as a circular structure on a lateral film, instead presenting as a series of vertical bones.